Described below is a method of transmitting data in a radio network with at least one sending station, at least one relay station and at least a first and a second receiving station, which data is organized in at least a first and a second layer. Furthermore, described below is a radio network having at least one sending station and at least one relay station, the radio network being designed to transmit data, which is organized in at least a first and a second layer, to at least a first and a second receiving station.
In modern telecommunication networks, high data rates are required to satisfy the demand of present-day applications. High data rates are achieved with high signal to noise ratios (SNR) in order to provide satisfactory bit error rates (BER). As the output power of sending stations normally is limited, relay stations are provided in some networks for this reason, which receive the data sent by the sending station and re-sent the data with a signal level higher than the level of the received signals. Relay assisted communication is a promising approach to enhance the throughput in cellular systems such as 3GPP-LTE or Wimax. This increase in throughput is achieved by decreasing the path loss attenuation of the shadowed users by use of a relay. The decrease in path loss improves the signal power distribution in the cell, and in turn increases the possible throughput. (3GPP LTE—Long Term Evolution—is the name given to a project within the Third Generation Partnership Project to improve the UMTS mobile phone standard to cope with future technology evolutions. WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology that provides for the wireless transmission of data in a variety of ways, ranging from point-to-point links to full mobile cellular-type access.)
In addition, more sophisticated methods to improve the data transmission exist in modern networks, such as multiple antenna systems combined with OFDM technology. One such example is improving the cell coverage area while maintaining good spectral efficiency. In MIMO-OFDM (MIMO=Multiple Input Multiple Output, OFDM=Orthogonal Frequency Division Multiplexing) spectrally efficient coverage enhancement is achieved by frequency dependent link adaptation and scheduling. In spite of the advancements made, the average achieved spectral efficiency becomes limited by the user distribution in the cell. For instance, high demand from users with bad channel conditions can cause problems in the spectrum. Such users with bad channel conditions could be for instance located in cell edge, deep shadowed areas or even indoors.
Recently, US 2008/0025323 Al has been published, which is related to this topic and discloses a system and method for a multi-layer multi-hop wireless system. In one example, the method includes dividing information to be sent from a source node to a destination node via a relay node into at least first and second segments. A signal containing the first and second segments is generated for transmission from the source node, where the first and second segments are encoded differently within the signal. The signal containing the first and second segments is sent from the source node to the relay node and the destination node. Only the first segment is recovered from the signal by the destination node, while the first and second segments are recovered by the relay node. The second segment is sent by the relay node to the destination node, which combines the first and second segments to reconstruct the information. The information may be organized in different layers, in particular layers with different priorities.